[Zope] calling getOwner on an ExtFile instance raises an Unauthorized ex ception

All, Does anyone know why calling getOwner() on an instance of ExtFile raises an unauthorized exception? Error Type: Unauthorized Error Value: You are not allowed to access 'getOwner' in this context ExtFile imports SimpleItem which, in turn, imports AccessControl.Owner Here's the code from ExtFile: from OFS.SimpleItem import SimpleItem Here's the code from SimpleItem: import AccessControl.Role, AccessControl.Owned, App.Common I've got some other custom objects in my application which import SimpleItem and I am able to call getOwner() on them no problem. Thanks, Tom